Infinite scroll in the repository list

app/src/main/java/fr/uca/iut/clfreville2/teaiswarm/MainActivity.kt

@@ -3,39 +3,26 @@ package fr.uca.iut.clfreville2.teaiswarm
 import android.content.Intent
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
-import android.widget.Button
+import androidx.fragment.app.Fragment
-import androidx.lifecycle.lifecycleScope
+import androidx.fragment.app.FragmentFactory
-import androidx.recyclerview.widget.RecyclerView
+import androidx.fragment.app.commit
+import fr.uca.iut.clfreville2.teaiswarm.fragment.RepositoryListFragment
 import fr.uca.iut.clfreville2.teaiswarm.model.Repository
-import fr.uca.iut.clfreville2.teaiswarm.network.GiteaService
-import kotlinx.coroutines.launch
-import kotlin.math.max
 
 const val REPOSITORY_OWNER = "repository_owner"
 const val REPOSITORY_NAME = "repository_name"
 
 class MainActivity : AppCompatActivity() {
 
-    private val service = GiteaService()
-    private lateinit var repositories: RecyclerView
-    private lateinit var previousButton: Button
-    private lateinit var nextButton: Button
-    private var currentPage = 1
-
     override fun onCreate(savedInstanceState: Bundle?) {
+        supportFragmentManager.fragmentFactory = RepositoryListFragmentFactory { repo ->
+            adapterOnClick(repo)
+        }
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
-        repositories = findViewById(R.id.repositories_view)
+        supportFragmentManager.commit {
-        previousButton = findViewById(R.id.previous_repository_list)
+            setReorderingAllowed(true)
-        nextButton = findViewById(R.id.next_repository_list)
+            replace(R.id.fragment_container_view, RepositoryListFragment::class.java, null)
-        updateList()
-        previousButton.setOnClickListener {
-            currentPage = max(currentPage - 1, 0)
-            updateList()
-        }
-        nextButton.setOnClickListener {
-            currentPage += 1
-            updateList()
         }
     }
 
@@ -46,12 +33,12 @@ class MainActivity : AppCompatActivity() {
         startActivity(intent)
     }
 
-    private fun updateList() {
+    class RepositoryListFragmentFactory(private val onClick: (Repository) -> Unit) : FragmentFactory() {
-        lifecycleScope.launch {
+        override fun instantiate(classLoader: ClassLoader, className: String): Fragment {
-            val repos = service.listActiveRepositories("clement.freville2", currentPage)
+            if (className == RepositoryListFragment::class.java.name) {
-            repositories.adapter = RepositoryListAdapter(repos) { repo ->
+                return RepositoryListFragment("clement.freville2", onClick);
-                adapterOnClick(repo)
             }
+            return super.instantiate(classLoader, className)
         }
     }
 }

app/src/main/java/fr/uca/iut/clfreville2/teaiswarm/adapter/RepositoryListAdapter.kt

@@ -1,14 +1,17 @@
-package fr.uca.iut.clfreville2.teaiswarm
+package fr.uca.iut.clfreville2.teaiswarm.adapter
 
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import android.widget.TextView
+import androidx.paging.PagingDataAdapter
+import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView
+import fr.uca.iut.clfreville2.teaiswarm.R
 import fr.uca.iut.clfreville2.teaiswarm.model.Repository
 
-class RepositoryListAdapter(private val dataSet: List<Repository>, private val onClick: (Repository) -> Unit) :
+class RepositoryListAdapter(diffCallback: DiffUtil.ItemCallback<Repository>, private val onClick: (Repository) -> Unit) :
-    RecyclerView.Adapter<RepositoryListAdapter.ViewHolder>() {
+    PagingDataAdapter<Repository, RepositoryListAdapter.ViewHolder>(diffCallback) {
 
     class ViewHolder(view: View, private val onClick: (Repository) -> Unit) : RecyclerView.ViewHolder(view) {
         private val repositoryNameView: TextView
@@ -72,8 +75,14 @@ class RepositoryListAdapter(private val dataSet: List<Repository>, private val o
     }
 
     override fun onBindViewHolder(holder: ViewHolder, position: Int) {
-        holder.bind(dataSet[position])
+        holder.bind(getItem(position))
     }
 
-    override fun getItemCount() = dataSet.size
+    object RepositoryComparator : DiffUtil.ItemCallback<Repository>() {
+        override fun areItemsTheSame(oldItem: Repository, newItem: Repository): Boolean =
+            oldItem.owner == newItem.owner && oldItem.name == newItem.name
+
+        override fun areContentsTheSame(oldItem: Repository, newItem: Repository): Boolean =
+            oldItem == newItem
+    }
 }

app/src/main/java/fr/uca/iut/clfreville2/teaiswarm/fragment/RepositoryListFragment.kt

@@ -0,0 +1,104 @@
+package fr.uca.iut.clfreville2.teaiswarm.fragment
+
+import android.os.Bundle
+import android.view.View
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.viewModels
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import androidx.lifecycle.lifecycleScope
+import androidx.lifecycle.viewModelScope
+import androidx.paging.*
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import fr.uca.iut.clfreville2.teaiswarm.R
+import fr.uca.iut.clfreville2.teaiswarm.adapter.RepositoryListAdapter
+import fr.uca.iut.clfreville2.teaiswarm.model.Repository
+import fr.uca.iut.clfreville2.teaiswarm.network.GiteaService
+import fr.uca.iut.clfreville2.teaiswarm.network.RepositoryService
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.launch
+import retrofit2.HttpException
+import java.io.IOException
+
+class RepositoryListFragment(private val username: String, private val onClick: (Repository) -> Unit) : Fragment(R.layout.repository_list) {
+
+    private val service = GiteaService()
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        updateRepositories()
+    }
+
+    private fun updateRepositories() {
+        val viewModel by viewModels<RepositoryViewModel>(
+            factoryProducer = {
+                RepositoryViewModelFactory(
+                    service,
+                    username
+                )
+            }
+        )
+        val pagingAdapter =
+            RepositoryListAdapter(RepositoryListAdapter.RepositoryComparator, onClick)
+        val recyclerView = requireView().findViewById<RecyclerView>(R.id.repositories_view)
+        recyclerView.adapter = pagingAdapter
+        recyclerView.layoutManager = LinearLayoutManager(requireContext())
+        viewLifecycleOwner.lifecycleScope.launch {
+            viewModel.flow.collectLatest { pagingData ->
+                pagingAdapter.submitData(pagingData)
+            }
+        }
+    }
+
+    class RepositorySource(
+        private val service: RepositoryService,
+        private val username: String
+    ) : PagingSource<Int, Repository>() {
+
+        override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Repository> =
+            try {
+                val nextPageNumber = params.key ?: 1
+                val response = service.listActiveRepositories(username, nextPageNumber)
+                LoadResult.Page(
+                    data = response,
+                    prevKey = nextPageNumber - 1,
+                    nextKey = nextPageNumber + 1
+                )
+            } catch (e: IOException) {
+                LoadResult.Error(e)
+            } catch (e: HttpException) {
+                LoadResult.Error(e)
+            }
+
+        override fun getRefreshKey(state: PagingState<Int, Repository>): Int? =
+            state.anchorPosition?.let { anchorPosition ->
+                val anchorPage = state.closestPageToPosition(anchorPosition)
+                anchorPage?.prevKey?.plus(1) ?: anchorPage?.nextKey?.minus(1)
+            }
+    }
+
+    class RepositoryViewModel(
+        private val service: RepositoryService,
+        private val username: String
+    ) : ViewModel() {
+        val flow = Pager(
+            PagingConfig(pageSize = 10, enablePlaceholders = true)
+        ) {
+            RepositorySource(service, username)
+        }.flow.cachedIn(viewModelScope)
+    }
+
+    class RepositoryViewModelFactory(
+        private val service: RepositoryService,
+        private val username: String
+    ) : ViewModelProvider.Factory {
+        override fun <T : ViewModel> create(modelClass: Class<T>): T {
+            if (modelClass.isAssignableFrom(RepositoryViewModel::class.java)) {
+                @Suppress("UNCHECKED_CAST")
+                return RepositoryViewModel(service, username) as T
+            }
+            throw IllegalArgumentException("Unknown ViewModel class")
+        }
+    }
+}

app/src/main/java/fr/uca/iut/clfreville2/teaiswarm/network/GiteaService.kt

@@ -1,7 +1,6 @@
 package fr.uca.iut.clfreville2.teaiswarm.network
 
 import com.squareup.moshi.Moshi
-import com.squareup.moshi.adapters.EnumJsonAdapter
 import com.squareup.moshi.adapters.Rfc3339DateJsonAdapter
 import com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterFactory
 import fr.uca.iut.clfreville2.teaiswarm.model.*
@@ -33,8 +32,12 @@ class GiteaService(private val handle: GiteaApiService) : RepositoryService {
     constructor() : this(createRetrofit().create(GiteaApiService::class.java))
 
     override suspend fun listActiveRepositories(username: String, page: Int): List<Repository> = withContext(Dispatchers.IO) {
+        if (page < 1) {
+            emptyList()
+        } else {
             handle.listActiveRepositories(username, page)
         }
+    }
 
     override suspend fun listCommits(
         repository: RepositoryIdentifiable,

app/src/main/res/layout/activity_main.xml

@@ -1,32 +1,13 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity">
 
-    <androidx.recyclerview.widget.RecyclerView
+    <androidx.fragment.app.FragmentContainerView
-        android:id="@+id/repositories_view"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        app:layoutManager="LinearLayoutManager"/>
+        android:id="@+id/fragment_container_view" />
-
-    <LinearLayout
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintStart_toStartOf="parent">
-        <Button
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:id="@+id/previous_repository_list"
-            android:text="@string/previous" />
-        <Button
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:id="@+id/next_repository_list"
-            android:text="@string/next" />
 </LinearLayout>
-</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/repository_list.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/repositories_view"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+</androidx.constraintlayout.widget.ConstraintLayout>